Picatinny Arsenal engineers have fired the newly modified M777A2 howitzer at Yuma Proving Ground, Arizona, completing the next step towards expanding the system’s current firing range.
“We put together an integration test bed for the M777A2 Extended Range (M777ER) howitzer program, incorporating a 55 caliber cannon tube on the M777A2 towed howitzer,” said Andy McFadzean a Special Project Officer at the U.S. Army Armament Research, Development and Engineering Center or ARDEC.
“We shot a total of 70 rounds using the Modular Artillery Charge System (MACS), zone two to zone six, propelling charge. This test marked the first time a MACS zone 6 was fired from the M777 howitzer. Previously, the top charge fired was a MACS zone 5.”
The modification added six feet to the cannon while limiting the increase in overall system weight to less than 1,000 pounds.
The total length of the tube increased the chamber volume as well as the rifling length. That, in combination with the additional increment of legacy propellant (MACS zone 6), resulted in an increase in range of several kilometers.
“We were able to push the round harder for longer, so it goes faster and further,” said David Bound, M777ER Team Lead.
“Think of it like a guy with a really long arm. He can hold a ball longer and throw it faster than a guy with a really short arm. So we just integrated that longer ‘arm’ onto the howitzer so that the same bullet could get acted on longer and quicker. That in turn means more range,” said Bound.
“The main point of the test was to build confidence,” said Bound “that’s not even the best range increase we can get, but there were some doubts that we could even go that far on the system.”
CRAWL, WALK, RUN
Project Manager Towed Artillery Systems and ARDEC are using an incremental approach to increasing the range of the M777A2 howitzer. The ultimate goal of the program is to demonstrate a maximum range of 70KM while minimizing the cost and modifications to the weapon platform.
The Army’s Extended Range Cannon Artillery (ERCA) program is investigating and developing technology to extend the range of the Army’s 155mm self-propelled howitzer. The M777ER program is integrating the ERCA technology onto the towed howitzer platform.
Initially, a non-firing, mobility platform was developed with an extended range cannon tube. The mobility trails successfully demonstrated that an M777ER howitzer could be towed behind its current prime mover with little modifications.
Upon successful completion of mobility trials, a firing demonstrator was created using the current 39 caliber cannon without a muzzle brake. The 39 caliber demonstrator put similar stress on the systems structures as a 55 caliber cannon with a muzzle brake. The test results of the 39 caliber demonstrator were used to validate engineering design models for the objective extended range weapon.
The latest configuration of the M777ER weapon integrated a 55 caliber cannon tube onto the weapon platform. The cannon tube was manufactured at the Army’s Watervliet Arsenal. The firings at Yuma in November 2016 marked the latest success in the M777ER program.
The engineers have planned additional incremental improvements with several demonstrations over the next few years.
“We’re not going to do all of our design work in a vacuum and show up in five years with a system the user hasn’t seen before,” said Bound.
“The latest test at Yuma was one of those steps. Several marines and soldiers were at Yuma in November to witness the firings,” said Bound. “I think they are all very happy and impressed with the fact that the M777ER did what it did so quickly and they are definitely excited to see the next step, which should be around July 2017. “We are taking a crawl, walk, run approach to keep the user involved through the whole process,” said McFadzean.
“Too many times we do a project like this and we think we know what they [the user] want. If we have them involved throughout the process it allows us to make the system more suitable to fit their needs,” said Bound.
The engineers thought weight would be a limiting factor, but it was not.
“It actually looks like the strength of the gun will be our limiting factor, which means we can design the M777ER to its engineering limit. Knowing the engineering limits of the system coupled with input from the user will allow designers to optimize the objective system,” said Bound.
“The latest test is certainly an intermediate step. We saw a few different outcomes then we expected to see. For example, the gun is very light so it moves when it shoots especially at low angles but we did not expect to see it move as much as it did. That wasn’t even on our radar as an outcome of the test. One thing we expected to see and didn’t was an increase in tube whip, the bouncing of the cannon tube after firing, but it appears the elevation system can lift all that additional weight and still hold the tube steady,” said Bound.
BLAST OVER PRESSURE
“Another concern we are dealing with is the blast over pressure,” said McFadzean.
“When the weapon is fired, it’s like setting off a very large firecracker. There is a blast wave that comes out of the muzzle. The muzzle brake, which is located at the end of the cannon tube, takes that energy of the extra propellant gases and redirects them backward so that it helps slow down the tube during recoil,” said Bound. “Think of it like a sail on the end of the cannon tube that’s catching all of that blast to slow the gun down.”
“Unfortunately, this redirects all that energy back at the crew and, if we redirect it too much, we hit the crew with a large blast wave that can hurt them. To reduce the impact on the crew, the engineers at Benet Laboratories are designing a muzzle brake that gets us the efficiency we require while keeping the crew safe and out of the way of all the redirected energy,” said Bound.
“Testing to date has been done with legacy ammunition which is what the soldiers and marines currently use every day. ERCA is also designing a new rocket assistant projectile and a new super charge,” Bound added.
“The next step is to see if the M777ER platform can take the force from the new ammunition since we would be going from a 7 kilometer increase in range to a 40 km increase in range. Once we prove that we can actually do this, a user evaluation will be conducted and feedback on any other modifications will be solicited. This can be expected around July of fiscal year 18,” said Bound.
The M777ER program is a collaborative effort between PEO Ammunition, PM TAS and ARDEC. ARDEC’s role is to provide the engineering to push the system to its limit to maximize range. The job of Program Manager Towed Artillery Systems is to work with the Soldiers, Marines and ARDEC to refine the systems requirement to make sure user expectations are met.
Filed Under: Aerospace + defense